/* com_writer.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <unistd.h>

#define BUFFER_SIZE 1024
char *dev[] = {"/dev/ttyUSB0","/dev/ttyUSB1","/dev/ttyUSB2","/dev/ttyUSB3","/dev/ttyUSB4"};

/*打开串口函数*/
int open_port(void)
{
	int fd,i;
	
	/* 打开串口 */
	for(i = 0; i < sizeof(dev)/sizeof(char*); i++)
	{
		fd = open(dev[i], O_RDWR|O_NOCTTY|O_NDELAY);
		if(fd < 0)
		{
			printf("%s\n",dev[i]);
			perror("open failed");
			continue;
		}
		else
		{
			break;
		}
	}	
	if (fd < 0)
	{
		perror("open serial port failed");
		return(-1);
	}
	else
	{
		printf("open serial port: %s successed!\n",dev[i]);
	}
	/*恢复串口为阻塞状态*/
	if (fcntl(fd, F_SETFL, 0) < 0)
	{
		perror("fcntl F_SETFL");
	}
	/*测试是否为终端设备*/
	if (isatty(STDIN_FILENO) == 0)
	{
		perror("standard input is not a terminal device");
	}
	return fd;
}
int set_com_config(int fd,int baud_rate,int data_bits, char parity, int stop_bits)
{
	struct termios new_cfg,old_cfg;
	int speed;
	/*保存并测试现有串口参数设置,在这里如果串口号等出错,会有相关的出错信息*/
	if (tcgetattr(fd, &old_cfg) != 0)
	{
		perror("tcgetattr");
		return -1;
	}
	/* 设置字符大小*/
	new_cfg = old_cfg;
	cfmakeraw(&new_cfg); /* 配置为原始模式 */
	new_cfg.c_cflag &= ~CSIZE;
	/*设置波特率*/
	switch (baud_rate)
	{
		case 2400:
			{
				speed = B2400;
			}
			break;
		case 4800:
			{
				speed = B4800;
			}
			break;
		case 9600:
			{
				speed = B9600;
			}
			break;
		case 19200:
			{
				speed = B19200;
			}
			break;
		case 38400:
			{
				speed = B38400;
			}
			break;
		default:
		case 115200:
			{
				speed = B115200;
			}
			break;
	}
	cfsetispeed(&new_cfg, speed);
	cfsetospeed(&new_cfg, speed);
	/*设置停止位*/
	switch (data_bits)
	{
		case 7:
			{
				new_cfg.c_cflag |= CS7;
			}
			break;
		default:
		case 8:
			{
				new_cfg.c_cflag |= CS8;
			}
			break;
	}
	/*设置奇偶校验位*/
	switch (parity)
	{
		default:
		case 'n':
		case 'N':
			{
				new_cfg.c_cflag &= ~PARENB;
				new_cfg.c_iflag &= ~INPCK;
			}
			break;
		case 'o':
		case 'O':
			{
				new_cfg.c_cflag |= (PARODD | PARENB);
				new_cfg.c_iflag |= INPCK;
			}
			break;
		case 'e':
		case 'E':
			{
				new_cfg.c_cflag |= PARENB;
				new_cfg.c_cflag &= ~PARODD;
				new_cfg.c_iflag |= INPCK;
			}
			break;
		case 's': /*as no parity*/
		case 'S':
			{
				new_cfg.c_cflag &= ~PARENB;
				new_cfg.c_cflag &= ~CSTOPB;
			}
			break;
	}
	/*设置停止位*/
	switch (stop_bits)
	{
		default:
		case 1:
			{
				new_cfg.c_cflag &= ~CSTOPB;
			}
			break;
		case 2:
			{
				new_cfg.c_cflag |= CSTOPB;
			}
	}
	/*设置等待时间和最小接收字符*/
	new_cfg.c_cc[VTIME] = 0;
	new_cfg.c_cc[VMIN] = 1;
	/*处理未接收字符*/
	tcflush(fd, TCIFLUSH);
	/*激活新配置*/
	if ((tcsetattr(fd, TCSANOW, &new_cfg)) != 0)
	{
		perror("tcsetattr");
		return -1;
	}
	return 0;
}

int main(void)
{
	int fd;
	char buff[BUFFER_SIZE];
	if((fd = open_port()) < 0) /* 打开串口 */
	{
		return 1;
	}
	if(set_com_config(fd, 115200, 8, 'N', 1) < 0) /* 配置串口 */
	{
		perror("set_com_config");
		return 1;
	}
	do
	{
		printf("Input some words(enter 'quit' to exit):");
		memset(buff, 0, BUFFER_SIZE);
		if (fgets(buff, BUFFER_SIZE, stdin) == NULL)
		{
			perror("fgets");
			break;
		}
		write(fd, buff, strlen(buff));
		if (read(fd, buff, BUFFER_SIZE) > 0)
		{
			printf("The received words are : %s", buff);
		}
	} while(strncmp(buff, "quit", 4));
	close(fd);
	return 0;
}
